The present invention relates generally to techniques of determining a path in dense wavelength division multiplexing (DWDM) networks.
DWDM networks are optical networks in which optical signals at different wavelengths share an optical fiber. Each wavelength defines a particular communication channel. In a stricter sense, DWDM also refers to an International Telecommunications Union (ITU) standard which includes the specification of the particular channel wavelengths and the spacings between these channels and is based upon wavelength division multiplexing (WDM), an earlier ITU standard in which the channel spacings were further apart and a smaller number of wavelength channels were carried by an optical fiber. It should be noted that the term DWDM, as used herein, generally refers to the first, more inclusive sense so as to include the ITU WDM and DWDM standards, unless specifically stated otherwise.
For communication to be established between the source of the communication and its destination in an electronic network that includes network nodes, a path must be selected through the network nodes. The network path is determined by the electronic control plane of the network that is formed from control units located at each node within the network. At each selected network node, there is a control unit which, linked to other control units at other nodes of the network, selects the path of a communication from the selected network node. The aggregate of the control units forms the control plane of the network which, after determining the path, sets up the path of a communication from its source to its destination through the network nodes. Common technologies for determining a communications path are, for example, Internet Protocol (IP), Frame Relay, Asynchronous Transfer Mode (ATM), and Ethernet. Additionally, other technologies which may be associated with path determination MultiProtocol Label Switching (MPLS), which fits over such older technologies as mentioned above, and generalized MPLS (GMPLS), which is a version of MPLS. An emerging standard for path determination is Path Computation Engine (PCE), a technology by which a server computes a path through the network.
Such electronic control plane technologies are adapted for electronic networks. Unlike electronic networks, however, within a DWDM network, both a physical path of a communication and its wavelength must be determined. Furthermore, the nature of the optical signals substantially requires that optical parameters, as for example, the attenuation, chromatic dispersion between the nodes and the like, be considered in the proper selection of an optical path to ensure that signals reach their intended destination in proper condition. Otherwise, the optical signals must be regenerated at one or more intermediate nodes between a source and its intended destination.